UPS ground saver currently does not show up in the rate browser when you are using your own UPS account. Support has confirmed that this is a short coming of Shipstation.
This is a basic feature of any shipping software and should be resolved quickly. I should be able to see all the available rates from all my UPS accounts. I can manually select it in the service selection, so it's available, it just doesn't show up in the rate browser. This makes it an extra step if I want to use Ground saver to ship.